It is known to use a so-called line-up clamp to that end, which clamp is moved within the pipes until on either side of the weld to be formed, and which, at that location, is brought into clamping engagement with the inner surfaces of the ends of the pipes to be welded together. The frame on which the clamping means for both pipes have been arranged provides a rigid orienting means, as a result of which the pipes will be exactly aligned before welding. Such an arrangement is for instance shown in Dutch patent application 90.02396. Here, after orienting the pipes an annular supporting frame for the welding equipment is placed at the outside of the pipes, using a mounting belt arranged earlier on on one of the pipes. For said technique, International patent application WO 95/21721 could also be referred to, in which document a line-up clamp which is mobile within the pipes is described.
The use of a line-up clamp which moves within the pipes requires special provisions, such as long operating lines, the length of which corresponds to the length of the pipe line made ready. Furthermore the line-up clamp has to be retrieved entirely in case it malfunctions. This results in considerable delays in the work.
It is an object of the invention to improve on this.